Method and system for failure prediction using lubricating fluid analysis

ABSTRACT

Methods and systems for failure prediction using analysis of oil or other lubricant. Raw data about feature(s) of each of a plurality of particles filtered from a fluid sample are used to categorize each particle into one of a plurality of categories, each category being defined by one or more of: chemical composition, size and morphology. Particle physical characteristics in each category are quantified to obtain a set of categorized data. The categorized data are compared with historical data. Results of the comparing are evaluated to generate a prediction of any failure or mechanism of failure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/661,181 filed on Oct. 26, 2012, the contents of which are herebyincorporated by reference.

TECHNICAL FIELD

The disclosure relates generally to methods and systems for failureprediction using fluid analysis, and more particularly to methods andsystems for failure prediction in engines using oil (or other lubricant)analysis.

BACKGROUND OF THE ART

The analysis of engine oil or other lubricant for the purpose ofidentifying premature component wearing has been performed for severaldecades using optical atomic spectroscopy (e.g., atomic emissionspectroscopy (AES), as well as its predecessor that has been in use as afield monitoring method, atomic absorption spectroscopy (AAS)). Thistechnology has been the basis for the military aviation's SpectroscopicOil Analysis Program (SOAP). However, this technology may havedisadvantages, such as a lack of repeatability among different equipmentand an inability to analyze particles greater than 5 μm in diameter.Furthermore, SOAP typically uses optical atomic spectroscopy, which isan elemental analysis of the total oil sample and typically does notcharacterize individual particles in the sample.

Rotrode Filter Spectroscopy has been introduced in 1980 and it wascommercialized by Spectro Incorporated (Littleton, Mass.). The methodfocuses mainly on the analysis of large particles in the oil and hasproven to be effective to establish the source of wear material in asystem already generating wear material [1].

Scanning electron microscope (SEM) equipped to perform X-rayspectroscopy has been used to characterize individual particles [2] forwear mode indicators. However, SEM has been considered to be unsuitablefor routine monitoring of machine condition, for example as reported inWhitlock [3].

SUMMARY

The disclosure describes methods and systems for failure predictionusing analysis of a fluid, such as oil or other lubricant. In variousaspects, for example, the disclosure describes methods and systems forfailure prediction using analysis of oil samples, such as from gasturbine engines.

In some example aspects, the present disclosure provides a method forfailure prediction in an engine, the method being implemented by aprocessor, the method may include: receiving raw data representing aplurality of features of each of a plurality of particles filtered froma fluid sample obtained from the engine, the engine belonging to anengine type; wherein the plurality of features includes at least onephysical characteristic and chemical composition; categorizing eachparticle into one of a plurality of categories according to at least oneof the plurality of features by calculating a likelihood that a givenparticle belongs to a given category, each category being defined by oneor more of: chemical composition, size and morphology; quantifyingparticle physical characteristics in each category to obtain a set ofcategorized data; comparing the set of categorized data with at leastone set of historical data associated with the engine type, thehistorical data being retrieved from a database; evaluating results ofthe comparing using a set of predefined rules to generate a predictionof any failure or mechanism of failure; and generating an outputindicating the prediction.

In some example aspects, the present disclosure provides a system forfluid analysis, the system may include a processor and a memorycontaining machine-readable instructions for execution by the processor,the machine-readable instructions causing the processor to carry out themethod described above.

In some example aspects, the present disclosure provides anon-transitory computer-readable medium or media embodyingcomputer-executable instructions configured for causing one or moreprocessors to carry out the method described above.

Further details of these and other aspects of the subject matter of thisapplication will be apparent from the detailed description and drawingsincluded below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying drawings, in which:

FIG. 1 is a flowchart illustrating an example of the disclosed methodsfor failure prediction using oil analysis; and

FIG. 2 illustrates an example of different alloy zones that may be usedfor categorizing particles.

DETAILED DESCRIPTION

Recently developed engines, such as gas turbine engines, may producedebris (e.g., metallic debris) in oil samples at a level ofconcentration below the operating zone of conventional oil analysistechniques (e.g., SOAP, which typically requires debris to be present onthe order of parts per million (ppm)). It would be useful to providemethods and systems for analysis of oil (or other lubricant or fluid)samples from such engines, for example for detection of debris at thepart per billion (ppb) level.

Oil analysis to perform predictive maintenance (e.g., on engines) hasbeen performed for more than fifty years but has not been very useful todetect abnormal behavior early in the process. For example, usingconventional techniques, failure is typically detected only severalhours before the problem occurs, resulting in the need for the engineoperator to submit oil sample at low time intervals (e.g., every 10 to50 hours) to have a chance to capture the indication of failure beforethe actual failure occurs. Such a high frequency of sampling may not bepractical or economical for an aircraft operator.

Considering the direct and indirect costs of any engine failure andunplanned engine removal, there is a need for methods and systems thatmay be able to predict failure sufficiently in advance, in order for theappropriate tasks, such as maintenance and/or decommissioning, to bescheduled and carried out.

The conventional approach for monitoring engine material wear is toperform an analysis on particles that were extracted from the enginefilter. Collected debris is then typically analyzed by SEM. This methodis typically costly because the engine filter is typically not reused.Further, such a method may not be practical considering that removingthe engine filter may be time consuming. For such reasons, among others,filter analysis typically is not performed frequently and is mainly usedto monitor engines already identified as potentially behavingabnormally. Filter analysis typically is not suitable for routinemonitoring of engines.

In various aspects and examples, the disclosed methods and systems mayallow for analysis of engine oil (or other lubricant) samples in orderto detect abnormal behavior, based on material wear, without having toremove the engine filter. The disclosed methods and systems may bereferred to as “Complete Oil Analysis Technology” (COAT).

The disclosed methods and systems may be based on the analysis ofrelatively small particles in oil that typically are not captured by aconventional 30 μm porosity filter. By extending the oil analysis toinclude smaller particles, the disclosed methods and systems may providebetter understanding of engine behavior, using a relatively small oilsample. For example, it has been estimated that there are, on average,about one thousand particles sized between 0.5 μm to 30 μm per typicalsample, which can be analyzed to predict engine behavior, and whichtypically are not considered in conventional filter analysis.

The disclosed methods and systems may thus provide a diagnostic andanalytical tool based on analysis of particles in fluids, such as engineoil or other lubricant, and may provide advance detection of prematurewear on specific engine parts and/or detection of failure mechanisms.The disclosed methods and systems may be suitable for failure predictionfor gas turbine engines operating in the field. The disclosed methodsand systems may be used for prediction of other wear events, includingprediction of events other than failure, using analysis of other fluidsamples, for example any suitable lubricating fluid. For example, thedisclosed methods and systems may be used to identify any contaminantsthat have been introduced into a lubricating system (e.g., by usage inabnormal conditions or by a problem during maintenance). The disclosedmethods and systems may also be used to detect any abnormal behavior ofan engine component in contact with a lubrication fluid system, forexample.

FIG. 1 is a flowchart illustrating an example of the disclosed methodsfor failure prediction using analysis of a fluid, such as engine oil orother lubricant. The example method may be carried out by any suitableprocessor, such as in a SEM workstation. The workstation may include oneor more input devices (e.g., keyboard and mouse) for receiving userinput, as well as one or more data ports and/or communication ports forreceiving external data (e.g., wirelessly or through wired connections)from other processors and systems. The workstation may also include oneor more output devices (e.g., one or more screens and/or printers) fordisplaying and/or providing a report of predicted failure mechanisms. Insome examples, some or all of the method may be automated.

At 105 a fluid sample (e.g., an oil or other lubricant sample from anaircraft engine) is obtained. In the example of an oil sample from anaircraft engine, the oil sample may be collected by the aircraftoperator. In some examples, more than one sample may be obtained fromthe engine. A relatively small amount of oil (e.g., 25 mL or less) maybe sufficient. The amount of oil sample obtained may be selected inorder to obtain a certain number of particles. For example, it may beknown or expected that a given engine should have a certain density ofparticles in the oil after a certain number of operating hours. Thevolume of oil sample obtained may thus be determined in order to obtainat least 1000 particles, for example. The frequency of sampling may bedetermined based on the flight hours per year, the maturity of theengine, the typical behavior of the engine type and/or the history ofunscheduled engine removal for that engine type, for example. The samplemay be obtained and prepared using any suitable method.

At 110, the sample is filtered using any suitable method to obtainparticles from the sample. For example, a collected oil sample may befiltered using a very fine filter, such as a 0.22 μm filter, in order tofilter out even very small particles (e.g., particles sized as small as0.5 μm in diameter or smaller). Using such a filter, a sample of about25 mL may produce a surface sample of about 16 mm in diameter. Theparticles obtained may range in size from about 0.5 μm to about 1600 μm,for example, although smaller or larger particles may also be obtained.The volume of oil sample filtrated and the size of the sample preparedmay vary, such as according to the number of particles in the oil. Thevolume of oil sample that is filtrated may be determined based on thetype of engine and/or the expected normal levels of particles in theoil. In some examples, the obtained density of particles may be 500particles per mm², which may be the maximum density that can be used, toreduce or avoid particles overlapping. It may be useful to reduce oravoid particles overlapping, since two or more particles that overlapwith each other may be incorrectly detected as one large particle, whichmay lead to incorrect identification and analysis. In some examples, asample may have about 5-10% of particles that may not be identifiable,typically due to overlapping, and which may be excluded from theanalysis. This exclusion rate may be acceptable.

At 115, each particle is analyzed to determine a plurality of features,such as determination of one or more physical characteristics (e.g.,shape and size) and/or chemical composition (e.g., alloy type andchemical composition). SEM may be used for this analysis, although anyother suitable methods may be used. The SEM may be coupled to an X-RayFluorescence (XRF) detector for carrying out particle analysis. Forexample, an automated SEM, such as that from Aspex Corporation, may beused. The automated SEM may not require the presence of a human toselect the particle that will be analyzed. Software and/or hardware inthe system may automatically recognize the presence of a particle andmay then automatically move the stage and the electron beam on theparticle to perform the particle analysis. The particle size may also bedetermined automatically. Any other suitable equipment may be used toperform this analysis.

A subset of the particles (e.g., 10% or less) may be analyzed whileensuring a good representation of the whole sample is captured. Theanalysis of the subset may be normalized to reflect the result for thefull sample.

For an average oil sample, about 1500 to 2000 particles may be analyzed.Suitable image analyzer software, such as those conventionally used withSEM, may be used to collect data about particle characteristics and/orcomposition. Analysis of each particle may produce a respective set ofdata for that particle, for example there may be up to 70 data pointsfor each particle, the data describing various features of the particle(e.g., size, shape and composition, among others). The total number ofdata points obtained from analysis of a single sample may besignificantly greater than in conventional oil analysis techniques.

The raw data obtained from this analysis may be further processed, inorder to account for any measurement error and/or the possible presenceof contamination. This further processing may be carried out bycategorizing the particles as described below.

At 120, each particle is categorized based on the determined features(e.g., physical characteristics and/or chemical composition). Theparticles may be categorized in different categories, which may bedefined according to one or more of: chemical compositions (e.g.,elemental and/or alloy composition), size and morphology. For example,morphology of a particle may be determined by calculating an aspectratio for the particle (e.g., length to width ratio, for example, wherea ratio close to 1 may indicate the particle is close to a sphericalshape while a larger value, such as 10, may indicate that the particleis close to a long fiber shape). For example, particles may be classedin a category such as “Environmental”, “Metallic”, “Non-metallic”,“Plating”, or “Miscellaneous”, among others. Each particle may befurther categorized into sub-category levels. As an example, the“Metallic” category may have a level 1 sub-category of “Copper”, withinwhich may be level 2 sub-categories of “Bronze” and “Brass”. In someexamples, five levels of decisions may be used to categorize eachparticle into a specific level (e.g., metallic, copper, bronze, leadedbronze or machining chip). Categorization of particles may be based on,for example, the absolute chemical composition, the ratio of someelements, the correlation between a specific standard and the particle,the size of the particle and/or the shape of the particle. Categoriesmay be defined according to different alloy compositions, associationwith one specific manufacturing process and/or association with oneparticular source (e.g., engine component), for example. Categories mayalso be defined by the elemental composition or single material of theparticles.

FIG. 2 illustrates an example of how categories may be defined withrespect to iron (Fe), chromium (Cr) and nickel (Ni) composition in analloy. The diagram is divided into different zones, corresponding todifferent categories. Dots on the diagram illustrate how exampleparticles fall within different zones. The zones may be associated witha particular alloy and/or expected sources of the alloy. For example,zone 15 may be associated with M50, a bearing material. A particle thatis categorized as belonging to the category of zone 15 may be expectedto originate from a bearing, and its presence may be predictive ofbearing wear and/or a failure mechanism related to bearing wear.

Categorization of each particle may be carried out using an algorithm tomatch each particle to the appropriate category. Each particle may becompared against a historical standard for a category, in order todetermine if that particle belongs in that category. Example algorithmsfor carrying out this categorization include the use of a CrossProbability Match (CPM) Index, as well as logical exclusion tests.

The CPM may be understood as an evaluation of the product of thelikelihood of the unknown particle to be the standard (PvS) and thelikelihood of the standard to be the unknown particle (SvP). In thisexample, the likelihood of a match may be based on an evaluation of theelemental composition of the particle compared to that of a historicalstandard for that category or sub-category.

An example version of CPM uses a linear model, which is based on alinear contribution of each element equal to its concentration. The CPMlinear model may be described by the equation:

CPM_(ij) = P_(j)vS_(i) × S_(i)vP_(j) × 100 where${P_{j}{vS}_{i}} = {\sum\limits_{k}^{n}\left( {{\min \left\lbrack {\frac{E_{p_{k}}}{E_{s_{k}}},\frac{E_{s_{k}}}{E_{p_{k}}}} \right\rbrack}^{2} \times N_{S_{k}}} \right)}$${S_{i}{vP}_{j}} = {\sum\limits_{k}^{n}\left( {{\min \left\lbrack {\frac{E_{p_{k}}}{E_{s_{k}}},\frac{E_{s_{k}}}{E_{p_{k}}}} \right\rbrack}^{2} \times N_{P_{k}}} \right)}$$N_{P_{k}} = {\frac{E_{P_{k}}}{\sum\limits_{l}^{n}\left( E_{P_{l}} \right)}\mspace{14mu} {and}}$$N_{S_{k}} = \frac{E_{S_{k}}}{\sum\limits_{l}^{n}\left( E_{S_{l}} \right)}$

and where i denotes the particle being categorized; j denotes thehistorical standard; n denotes the number of elements of interest usedto categorize the particle; Ep_(k) denotes the concentration of theelement k in the particle being categorized; Es_(k) denotes theconcentration of the element k in the historical standard being comparedto; Np_(k) denotes the normalized concentration of the element k in theparticle being categorized; Ns_(k) denotes the normalized concentrationof the element k in the historical standard; Tp denotes the summation ofthe concentration of all elements of interest in the particle; Tsdenotes the summation of the concentration of all elements of interestin the historical standard; PvS denotes the probability for the particleto be the historical standard; and SvP denotes the probability for thehistorical standard to be the particle.

Another example model is CPMQ, the square root version of CPM, which isbased on a contribution equal to the squared of its concentration. CPMQmay be used where an element is present in a high percentage (e.g.,greater than 5%) in an alloy belonging to the category of interest. TheCPM square root model may be described by the equation:

CPMQ_(ij) = P_(j)vS_(i)^(*) × S_(i)vP_(j)^(*) × 100 where${P_{j}{vS}_{i}^{*}} = {\sum\limits_{k}^{n}\left( {{\min \left\lbrack {\frac{E_{p_{k}}}{E_{s_{k}}},\frac{E_{s_{k}}}{E_{p_{k}}}} \right\rbrack}^{2} \times N_{S_{k}}^{*}} \right)}$${S_{i}{vP}_{j}^{*}} = {\sum\limits_{k}^{n}\left( {{\min \left\lbrack {\frac{E_{p_{k}}}{E_{s_{k}}},\frac{E_{s_{k}}}{E_{p_{k}}}} \right\rbrack}^{2} \times N_{P_{k}}^{*}} \right)}$${N_{P_{k}}^{*} = \frac{\sqrt{E_{P_{k}}}}{\sum\limits_{l}^{n}\left( \sqrt{E_{P_{l}}} \right)}}\mspace{14mu}$$N_{S_{k}}^{*} = \frac{\sqrt{E_{S_{k}}}}{\sum\limits_{l}^{n}\left( \sqrt{E_{S_{l}}} \right)}$

Using CPM or other suitable statistic techniques to categorize eachparticle may allow for automation of particle categorization, forexample. Use of CPM or other suitable statistical techniques may alsoallow for categorization of particles while accounting for possiblemeasurement noise and/or contamination, for example.

In some examples, a category (also referred to as a group of interest)may further break down into one or more bins defined according toparticle size ranges. For example, particles may be categorized incolumns according to size (in μm, in the example shown) and in rowsaccording to composition. In some examples, particles may also be sortedinto bins according to particle morphology. In some examples, there maybe 84 categories and sub-categories. The categories may be defined basedon elemental composition, alloy type, particle origin, or any othersuitable category of particle characteristics and composition.Categorizing particles by size and/or shape, as well as composition mayallow for distinguishing between one failure mechanism that ischaracterized by small particles of a given alloy and a differentfailure mechanism that is characterized by large particles of the samegiven alloy, for example. Categorizing particles into categories otherthan simple elemental composition may also allow for discerning particledata patterns that may not be otherwise observed.

For example, a category may represent a generic type of alloy, and mayinclude one or more levels of sub-categories that may further split thecategory into finer categorization, for example as precisely as thealloy unified number (UNS) of the particles analyzed. For example, aspecific alloy may cover two or more categories and/or sub-categories.

Example categories and sub-categories include:

Environmental-sub-categories: calcium, sodium, CalSil (which mayoriginate from cement from an airstrip), dust-earth, talc, vermiculite(which may originate from packaging of the sample) and chlorides (withfurther sub-category NaCl).

Metallic-sub-categories: iron (which may include further sub-categoriesof different composition zones such as different steels, and other alloytypes), nickel, titanium, copper (with further sub-categories such asbrass, bronze and leaded copper), zinc (which may originate fromgalvanized coating found in the engine filters and is typically foundwith iron and phosphorus particles also), aluminum, magnesium, cobaltand chromium.

Non-metallic-sub-categories: aluminum/silicon, silicon/aluminum,silicon/magnesium, magnesium/aluminum, fiberglass, asbestos, filterfibers, glass beads and silica.

Others-sub-categories: MoS₂, grease with MoS₂, lead and contaminatedsilver.

Plating-sub-categories: tin, silver, cadmium, copper,phosphate-manganese (AMS 2481) and chromium.

Not categorized

These example categories may be predefined based on knowledge orexpectation of what particles would be obtained from an oil sample of agiven engine type. The categories may also be defined based on theanalysis of the samples. For example, if it appears that most of theparticles fall into a few categories, sub-categories may be defined forthose few categories in order to more finely categorize the particles.The defined categories may be different for different engine typesand/or at different total operating hours, for example.

At 125, the data obtained from categorization of particles is comparedwith historical data associated with the engine type and/or any datafrom previous analyses of the same engine. This comparison may be basedon a quantification in each category (e.g., a count of particles ofcertain characteristics, such as certain size and/or morphology, whichmay be based on the sorting of particles into bins within each category,and may include normalizing the count to a 25 mL sample and for 100% ofthe area analyzed), to obtain a set of categorized data. The categorizeddata in each category and/or sub-category, as well as categorized datarepresentative of all categories, may be compared with the historicaldata.

In an example where an oil sample from an engine is being analyzed, dataobtained for the specific oil sample may be compared with otherhistorical data obtained from engines of the same or similar typeobtained at equivalent or similar operating hours and/or equivalent orsimilar operating conditions (e.g., running in a dry or sandyenvironment vs. a wet environment).

Historical data may be collected as part of the disclosed methods andsystems, may be collected using other techniques, may be collected aspart of routine maintenance, may be derived from previous records andengine specifications, or may be obtained by any other suitable means.One or more sets of historical data may be represented by an aggregateor general historical model of expected engine wear and/or failuremechanisms for engines of a particular engine type. The historical modelmay be a simple average of all data for a given engine type at a givenoperating age, for example. In some examples, a historical model mayinclude an average of all data, expunged of six-sigma results. The modelmay be adjusted over time as more historical data sets are added to themodel. A model based on a larger population of historical data may be amore accurate and precise predictor of engine failure than a model basedon a smaller population of historical data. Historical data may includedata from different engines of the same engine type at the same orsimilar operating hours (also referred to as latitudinal data orcross-sectional data), and may also include data from the same engine atdifferent operating hours (also referred to as longitudinal data).

The comparison between the sample data and the historical data may becarried out using any suitable statistical methods. For example, anycategory with sample data values that fall outside a three sigma rangeof the historical data may be flagged or highlighted. For example, for agiven category the comparison may use the calculation: (sampledata—average data)/standard deviation.

In some examples, a composite variation value may be calculated based onthe difference between the sample and historical data, for exampleexpressed in standard deviation and/or a weight assigned to eachcategory. For example, a composite index for a low alloy may becalculated as:

${CI}_{LowAlloy} = {\sum\limits_{i = 10}^{12}\left\lbrack {\sum\limits_{j = 1}^{5}{w_{ij}S_{ij}}} \right\rbrack}$

Where: i is the zone category; j is the particle size category; S_(ij)is the deviation expressed in standard deviation for the particles ofthe category size j from the zone i; W_(ij) is the weight attributed forthe particles of the category size j from the zone I, and the sum of allweight is equal to 1. The weighting factor may be based on historicaldata and/or the engine model.

At 130, a prediction of any possible future failure and/or failuremechanism is generated. This prediction may be based on the results ofthe comparison with historical data. For example, a category flagged asbeing outside a three sigma range of the historical data may beconsidered to be predictive of failure of an engine part associated withthat category. This may be based on trend analysis of analysis resultsfrom the same engine or engine type. Corrective action (e.g., engineremoval or increased frequency of testing) may be determined based onthe engine history and/or expected performance of the engine type, forexample. In some examples, prediction of expected failure and/or failuremechanism may involve review by an export, a technical specialist and/oran operator. Examples of predicted mechanism of failure include excessvibration, bearing wear, external contamination following enginemaintenance, bearing rubbing, gear degradation, and bearing cage andrace degradation, among others

A prediction of failure may be based on a combination of two or morefactors. For example, comparison results that indicate a given enginehas a greater than normal number of small particles in ferrous alloyzone 20 (corresponding to stainless steel) may indicate excessive enginevibration. This result, in addition to comparison data that indicatesthe engine has an increased number of particles in zone 21(corresponding to the bearing cage) and submicron particles in zone 15,may together indicate that the engine is exhibiting problems with thebearing, compared to historical data.

A particular engine type may be known to have certain failure patterns,based on historical data. By comparing data for a given engine belongingto that category/sub-category with historical data for thatcategory/sub-category, a prediction may be generated to indicate whenthe given engine is expected to fail and/or the expected failuremechanism for the given engine. For example, historical data may revealcertain patterns of particle characteristics over time. By comparing thesample particle data of the given engine with the historical patternover time, a prediction may be generated of where the given engine is inthe expected timeline for engine failure.

In some examples, two or more engine types may share the same or similarmechanism of failure. In such cases, historical data of one engine typemay be used for failure prediction of the other engine type, historicaldata of two or more engine types may be compiled together, and/or thesample historical data may be used for failure prediction of two or moreengine types, for example.

Using the generated prediction of failure, appropriate action may betaken. For example, where failure of a particular part has beenpredicted, that part may be replaced and/or monitored with greaterfrequency. Or, where failure of the engine has been predicted, thatengine may be placed on a tighter maintenance and/or oil analysisschedule. For example, the disclosed methods may include performing amaintenance or pre-maintenance action on the engine. Maintenance orpre-maintenance actions that may be performed include, for example,flagging the engine for maintenance (e.g., in a maintenance file),generating a notification to alert a user for the need to performmaintenance, scheduling maintenance for the engine, and performing theappropriate maintenance, among others. The maintenance orpre-maintenance action performed may be dependent on the generatedprediction.

The generated prediction may be recorded and saved for further actionand/or future reference. The results may also be added to the historicaldata. An electronic image of the sample may also be stored for futurereference and/or further processing.

The present disclosure also provides systems for carrying out thedisclosed methods. An example system may include one or more processors(e.g., in a desktop computer, a handheld computer, a workstation, or anyother suitable computing device) that executes instructions (e.g., codeembodied in a memory coupled to the processor, or in a computer programproduct such as a CD, DVD or removable memory) in order to carry out thedisclosed methods. The system may include one or more apparatuses forcarrying out the particle analysis (e.g., apparatus for SEM and/or XRF,including any suitable energy dispersive spectrometer (EDS)). The systemmay also include one or more memories and/or databases for storing thehistorical data and/or records of generated predictions of failure.

The present disclosure also provides computer program products andnon-transitory computer-readable media, such as a CD, a DVD, and aninternal or external memory, embodying computer-executable instructionsfor carrying out the disclosed methods.

The disclosed methods and systems may allow for monitoring of an engineover time, and may allow for a timeline of expected failure mechanismsto be developed for that engine type.

The disclosed methods and systems may allow for more sensitive and/orearlier detection of possible engine failure, compared to conventionalmethods. For example, current oil analysis technologies may not identifythe composition of each particle, and a relatively high concentration(e.g., more than 10 ppm) of wear metal in the oil sample may be requiredto detect the presence of abnormal wearing. In some examples, thedisclosed methods and systems may allow the detection limit of wear inbearing material to be reduced by a factor of 1000 or more, which mayallow for earlier detection of a problem.

In the disclosed methods and systems, the size of the particles may alsobe taken into account, which may help to avoid potential error caused bythe presence of one big particle. For example, a spherical particle ofgear material that is 4 pm in diameter will give the same % Fe readingfor the total sample as 500 particles of bearing material each 0.5 μm indiameter. If the sizes of the individual particles are not taken intoaccount, this would lead to possible misdiagnosis of bearing wear asbeing gear wear.

The conventional SOAP technique typically relies on elemental analysisusing emission/atomic absorption analysis of particles. The particlesanalyzed are typically limited to 2-3 μm or smaller. The result of SOAPis typically a quantification of elements (e.g., iron) by volume (e.g.,in ppm), without a consideration of particle size, alloy type or shapeof the particle, and may produce a relatively small number of datapoints (e.g., about 30 data points that describe the total quantities ofindividual elements in the total sample). In the present disclosure, inadditional to categories defined by elemental composition, categoriesmay be defined in other ways, such as by alloy type and expectedparticle origin (e.g., specific engine component that might be thesource of the particle), as well as by particle size and shape. Theseother category definitions may help in identifying data patterns thatmay not be discernible when categorizing particles only by elementalcomposition. Further, the presently disclosed methods and systems mayconsider characteristics of each individual particle, rather thanoverall characteristics of the total sample.

Conventional oil analysis techniques typically are limited to analysisof relatively large particles (e.g., 30 μm or larger). The presentlydisclosed methods and systems may allow oil analysis to be carried outon large as well as smaller particles.

Further, conventional techniques typically considered SEM to beunsuitable for routine monitoring of engines. For example SEM typicallywas considered to be time-consuming and labor-intensive.

In various aspects and embodiments, the present disclosure may providethe ability to identify the composition of wear metal in an oil sample.In some examples, the disclosed methods and systems may provide a lowdetection limit that may allow the detection of abnormal wearingsufficiently early in the deterioration cycle, giving a chance to fixthe problem during a planned maintenance. Early and/or rapid detectionof a problem may also give the opportunity to fix the root cause of theproblem early, which may help to reduce the total number of problematicengine in the field.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.For example, although the disclosed method has been described in termsof a number of steps, certain steps may be omitted and/or rearranged inorder. Although the present disclosure makes reference to oil analysisfor predicting failure in an engine, analysis of other fluids (e.g.,other lubricants) for failure prediction in other components may becarried out using the disclosed methods and systems. Still othermodifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

REFERENCES

[1] M. Lukas, D. P. Anderson, Spectro Incorporated, Littleton, Mass.“Rotrode Filter Spectroscopy, Does It have a Place in Commercial orMilitary Oil Analysis Laboratory”.

[2] K. J. Eisentraut, R. W. Newman, C. S. Saba, R. E. Kauffman, and W.E. Rhine, “Spectrometrix oil analysis: detecting engine failures beforethey occur”, Analytical Chemistry 56, Aug. 84, 1086A-1094A.

[3] R. R. Whitlock, Advances in X-Ray Analysis, Volume 40, 1996.

1.-20. (canceled)
 21. A method for generating a failure prediction foran engine of an engine type, the method comprising: receiving a sampleof lubricant fluid collected from the engine, the sample of lubricantfluid having particles suspended therein; filtering out a plurality ofthe particles from the sample of lubricant fluid; using X-rayspectroscopy, analyzing the filtered particles and producing raw dataabout the filtered particles, the raw data including chemicalcompositions of individual filtered particles; using one or moreprocessors and the raw data: categorizing individual particles intocategories to generate categorized data, at least one category beingdefined by a chemical composition zone within a three-chemical-elementsystem; comparing the categorized data with historical data associatedwith the engine type; generating a failure prediction based on thecomparison and predefined rules, the failure predication beingindicative of one or both of the following: when the engine is expectedto fail and a mechanism of failure of the engine; and generating anoutput indicative of the failure prediction.
 22. The method of claim 21,wherein the raw data includes sizes and morphologies of individualfiltered particles.
 23. The method of claim 21, wherein the filteredparticles include particles smaller than about 30 μm in diameter. 24.The method of claim 21, wherein the filtered particles include particleshaving a size between about 0.5 μm and about 1600 μm in diameter. 25.The method of claim 21, wherein at least one category is definedaccording to a particle source.
 26. The method of claim 21, wherein thecomparison comprises at least one of a calculation of deviation of thecategorized data from the historical data, and a calculation ofvariation of the categorized data from the historical data.
 27. Themethod of claim 21, wherein the comparison comprises at least one of acomparison of the categorized data in each category to the historicaldata, and a comparison of a composite of the categorized data to thehistorical data.
 28. The method of claim 21, wherein the failureprediction is indicative of premature wear of an engine component. 29.The method of claim 21, wherein the failure prediction is indicative ofexcessive vibration.
 30. The method of claim 21, wherein the failureprediction is indicative of contamination following engine maintenance.31. The method of claim 21, wherein the failure prediction is indicativeof gear degradation.
 32. The method of claim 21, wherein the failureprediction is indicative of bearing degradation.
 33. The method of claim21, wherein using X-ray spectroscopy includes using X-ray fluorescence.34. The method of claim 21, wherein the sample of lubricant has a volumeof 25 ml or less.
 35. The method of claim 21, wherein the sample oflubricant contains at least 1000 particles.
 36. The method of claim 21,comprising analyzing each filtered particle and producing raw data abouteach filtered particle.
 37. The method of claim 21, comprisinggenerating the failure prediction based on a number of particles in oneof the categories.
 38. The method of claim 21, wherein the filteredparticles include non-metallic particles and the raw data includes dataabout the non-metallic particles.